This invention relates to a rotor assembly and, in particular, to an impeller drive shaft arrangement wherein the number and order of impellers mounted upon a single drive shaft can be arranged or rearranged without having to remove the shaft from its support structure. More specifically, this invention relates to an impeller mounting arrangement for use in a centrifugal compressor for providing wide flexibility in compressor staging whereby a number of different flow ranges can be attained utilizing a common base frame machine configuration.
Compressors, particularly those operating in a flow ranges between 700 and 3000 cfm, are being called upon by industry to perform an increasing number of tasks. As a result, the trend in this type of compressor has been towards "packaged" units capable of being modified to meet specific application requirements. One approach has been to package the rotor and coacting stationary compressor components in a cartridge. The cartridge is receivable in a base frame containing common machine components such as the intercoolers, oil supply, drives, controls and the like. This concept is disclosed in U.S. Pat. No. 3,802,795. Although the cartridge approach provides for some commonality in the base frame parts, it nevertheless requires that a new and relatively different cartridge be employed for each flow range serviced.
In order to overcome some of the disadvantages found in the cartridge concept, a modular approach has been developed providing for greater commonality between interchangeable parts. The apparatus of the present invention plays an important part in this modular approach in that it permits the compressor impellers to be interchangeably supported upon an impeller drive shaft that is carried within a common base frame. Impeller mounting is accomplished in a manner wherein the drive shaft does not have to be removed from its support journals or otherwise decoupled from the machine drive.